This invention relates to implantable medical devices for therapeutic or diagnostic uses such as endocardial cardiac pacemaker leads and/or cardioverter/defibrillator leads. There are various types of transvenous pacing and cardioversion or defibrillation leads developed for introduction into different chambers of a patient's heart. These implantable leads are usually constructed with an outer biocompatible insulating sheath encasing one or more conductors, one of which is typically attached at its distal end to an exposed tip electrode.
The tip electrode is usually placed in contact with endocardial tissue at the chosen site of the heart chamber by percutaneous introduction and passage through a venous access, often the sub-clavian vein or one of its tributaries, which leads to the heart chamber. As the lead is implanted into the patient, one typical response to this implantation is the fibrotic encapsulation (e.g., protein encapsulations) of the lead. The presence of fibrotic encapsulation can compromise the performance of the lead, especially in more permanent implantation situations. Furthermore, during the removal of the lead, it is typical to require a surgical procedure to remove a portion of the lead. For example, after a portion of a lead is excised from its position, a suspended weight (approximately 5 lbs) is attached to the exposed portion of the lead to allow for an application of a constant force over a period of several hours to extract the lead from the fibrotic encapsulation. Such removal procedure creates discomfort and pain to the patient.
It has been shown in the literature that modification of a plastic (e.g., polyethylene and polyetherurethane) with superoxide dismutase mimic (SODm) results in a significant reduction in fibrotic encapsulation in an implanted foreign device. See “Modification of Inflammatory Response to Implanted Biomedical Materials In Vivo by Surface Bound Superoxide Dismutase Mimics” authored by Kishore Udipi, et. al, Journal of Biomedical Material Research 2000, Sep. 15, 51(4):549-60. The method contemplated by Udipi does not result in a high density grafting of SODm on the surface of the plastic and is dependent on the composition of the substrate.
It would be a significant advantage to provide endocardial cardiac pacemaker leads and/or cardioverter/defibrillator leads or other medical device component having SODm surface treatment with improved bondability and densities, on a variety of substrates including those difficult to modify such as fluoropolymers.